The present invention relates to a process for the preparation of rubber laminates. More particularly, the present invention relates to a process for the preparation of rubber laminates, which comprises contacting a fluororubber containing specific compounding additives with a nitrile group-containing polymer rubber and bonding them by curing.
Recently, an increasing importance is attached to the resistance to alcohol-mixed gasoline and sour gasoline as the characteristics required of fuel hoses.
A fluororubber is excellent in the resistance to heat, oil, solvent and chemicals, and is used as a rubber excellent in the resistance to alcohol-mixed gasoline and sour gasoline.
Although the fluororubber has these excellent properties, it is more expensive than other rubbery materials such as an acrylonitrile/butadiene rubber, an epichlorohydrin rubber and a nitrile group-containing, highly saturated polymer and is defective in that the cold resistance is poor.
Accordingly, a material formed by laminating a layer of a fluororubber composition having the above-mentioned excellent characteristics on a layer of an ordinary rubber composition attracts attention. However, the fluororubber can not be bonded by curing to other rubber according to customary procedures, or the bonding force is very weak. Therefore, any laminate having a high bonding strength has not been obtained.
As the means for improving the curing bonding force to a fluororubber, there have been proposed a process in which a metal oxide and a silica filler and/or an epoxy resin are incorporated in an acrylonitrile/ butadiene rubber (see Japanese Patent Application Kokai Publication No. 56-53066) and a process in which a 1,8-diazabi-cyclo[5,4,0]undecene-7 salt of a carboxylic acid is further incorporated (see Japanese Patent Application Kokai Publication No. 58-162335).
According to these processes, however, it is impossible to bond the fluororubber firmly to the nitrile group-containing polymer rubber by curing, and no perfect technique has been developed.